1. Field of the Invention
The present invention relates to vehicle brake shoes of the type suitable for use with a drum brake system and, more particularly, to an improved brake shoe assembly which facilitates the replacement of the shoe lining without complete removal of the shoe assembly from mounted installation within the drum.
2. Description of the Prior Art
Conventional drum brake systems employ generally arcuate brake shoes mounted within a drum and connected to a bell crank actuator mechanism which forces the shoes into frictional contact with the inner surface of the drum when braking of the vehicle is desired. In many applications, such as semi-trailers, for example, the brake shoe comprises a pad of friction material riveted to a platform member which in turn is welded to a pair of webs. The webs are configured to support the shoe about the axle of the vehicle for pivotal movement by the bell crank actuator mechanism. Frequently, in such an application, the inboard side of the drum is protected by a removable inspection cover, or dust plate, permitting accessibility to the brake shoe components. However, when the brake shoe linings become worn and require replacement, the shoes cannot be removed from the inboard side of the drum. Instead, the vehicle must be placed on a jack, the wheel or wheels must be dismounted from the drum, the drum and wheel bearings must be removed from the axle, and the brake shoes together with their mounting hardware must be dismounted from the axle. The foregoing brake service procedure is not only time consuming, particularly with dual wheel vehicles, it is accompanied by possible risk of damage to the oil seals which protect the wheel bearings. As a consequence, the procedure involves considerable skill.
To minimize the time and expense associated with replacing brake shoes by conventional procedures, a type of brake shoe assembly is known wherein the lining may be disassociated from the brake shoe platform and webs. Such a shoe assembly is disclosed, for example, in U.S. Pat. No. 3,941,222, issued to Newstead on Mar. 2, 1976. In such a shoe assembly, the lining is bonded to a backing plate having a plurality of tongues which detachably cooperate with corresponding slots in the brake shoe platform to permit the liing to be selectively attached and detached from the shoe, allowing the brake linings to be renewed without removal of the entire shoe from mounted condition with respect to the axle. However, known shoe assemblies of the foregoing type involve the disadvantage that the lining is not firmly secured to the shoe platform and can, with use, become detached from the shoe. In addition, when brake shoes having detachable linings are to be renewed, the brake drum must, in the usual case, be removed because sufficient clearance is not available to disassociate the lining from the shoe with the shoe assembly installed within the drum. Therefore, it would be desirable to provide a shoe assembly having a replaceable lining which is securely fixed to the shoe but is conveniently removable from the shoe through the dust cover, or inboard side of the wheel assembly.